The present invention relates to apparatus for shifting main nozzles on a fluid-jet loom, and more particularly relates to an improvement in the main nozzle shifting system in which two or more main nozzles for weft insertion are arranged on the lathe of a fluid-jet type loom and shifted in position for the purpose of different color alternate weaving.
In the different color alternate weaving, wefts of different color have to be inserted into warp sheds in an alternate fashion. To this end, two or more sets of main nozzles, one for each weft, are provided on one end section of the lathe so that, at each weft insertion, one of the main nozzles is registered at an operative position facing the entrance to the weft transportation channel formed by an air guide or reed array arranged along the length of the lathe.
In the conventional system, this shifting in position of the main nozzle is effected by moving them horizontally in the warp direction. As later described in more detail, this mode of shifting requires movement of the main nozzle transversely of a vertical plane including the air guide or reed array and such transverse movement prevents close arrangement of the main nozzles to the air guide or reed array, while causing unstable weft transportation. The horizontal movement of the main nozzles in the warp direction further induces undesirable generation of tension or slack on the yarns caught by the main nozzle, which again mars the stable nature of the intended weft insertion.
In order to remove the above-described drawbacks inherent in the horizontal main nozzle shifting system, it is proposed in Japanese Patent Publication 55-142747, corresponding to U.S. Pat. No. 4,326,565, to shift the position of a number of main nozzles by providing them with a sort of rotary motion. In this proposal, a number of main nozzles are arranged around a common support shaft and the ejection terminals of the main nozzles are converged towards and located close to the entrance to the weft transportation channel formed by an air guide or reed array. As the support shaft rotates, ejection terminals of the main nozzles are moved along arcuate loci so that they can be alternately registered at the operative position facing the entrance to the weft transportation channel.
This prior construction, however, is accompanied with several fatal drawbacks. The converged arrangement of the main nozzle terminals naturally requires a curved construction of each main nozzle and, accordingly, a curved path of travel for the yarn through the main nozzle. Increased frictional resistance on the yarn caused by the curved construction requires higher pressure of the weft transporting jet fluid, and causes generation of fluffs on the yarn or, in the worst case, breakage of the yarn being processed.
Further, attention should be directed to the point that the ejection terminals of the main nozzles are moved along the arcuate loci but not along any straight locus. In order that the weft transporting jet-fluid ejected by each main nozzle can be fully received in the weft transportation channel, the direction of the main nozzle terminal should precisely meet that of the weft transportation channel. This means that registration of each main nozzle at the above-described operational position must be precisely timed to ejection of the jet fluid. Even a slight time slip in the registration of the main nozzles leads to ejection of the jet fluid off the entrance to the weft transportation channel while resulting in poor driving force for weft transportation. In order to avoid this trouble while allowing the ejection terminals to move along the above described arcuate loci, extremely subtle adjustment of the main nozzle shifting system and its operation is required, which is almost infeasible without intensive time consumption and highly trained labor for maintenance.